Can anyone give me any names of good books on agnosticism?

I am mostly an agnostic theist, but I am uncertain about my beliefs in the religious department. I don't like books that bash anyone whether religious or not. I'm not in full disbelief, but nor do I worship anyone. Can someone give me the name of a really good book on agnosticism or on how to feel okay about a lack of faith? My whole family is highly religious and constantly make me feel like crap for my lack of faith. I wanted a book that I could read that would give me some insight and varify that it is okay to not be Christian.